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Lesson 5: Navigation Instruments
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AGENDA: –Measurement of Depth –Measurement of Direction –Measurement of Distance –Measurement of Speed Applicable reading: Hobbs pg. 110-128. Lesson 5: Navigation Instruments
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Measurement of Depth Echo Sounder (fathometer) Hand leadline
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Lead Line Manual method of determining depth Also allows for a sampling of the bottom type
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Measurement of Direction Bearing: the horizontal direction of one terrestrial point as measured from another, expressed as an angle from 0 to 360 degrees. There are three references for bearings: –Relative –Magnetic –True
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000T / 270R 090T / 000R 180T / 090R 270T / 180R
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Visual Bearings can be measured in: - Degrees Relative ( # # # 0 R ) - Degrees Magnetic ( # # # pstgc OR 0 M ) - Degrees True ( # # # 0 T) The navigator must convert any of these types of bearings to True before they can be plotted on the chart. Measurement of Direction
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Azimuth or Bearing Circle Telescopic Alidade Bearing Circle/Alidade
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Telescopic Alidade Bearing Circle
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Measurement of Distance Radar - Distance is obtained by a radio wave that is transmitted into the air and returns as an echo. The time interval between transmission and return can be converted into a physical range. Used for distance (range) only!! Not normally used for bearings
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Measurement of Distance STADIMETER Used to determine precise ranges between ships in formation
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Making an Observation with the Stadimeter Distance is determined by: distance = height of object / tan (angle)
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Parallel Ruler Plotting Instruments
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Parallel Plotter Plotting Instruments
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Parallel Motion Protractor Plotting Instruments
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Compass Dividers Plotting Instruments
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Nautical Slide Rule Plotting Instruments
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Given two of the following, find the third: –Speed –Distance –Time Operation of Nautical slide Rule
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Measurement of Speed Speed over Ground (SOG) = true speed Speed through the water SPEED OVER GROUND Direct output of many electronic navigation systems (GPS, Loran) SPEED THROUGH WATER Impeller Log Pitotmeter Log Doppler Speed Log Shaft RPM
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Measurement of Speed Impeller Log
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Measurement of Speed Pitometer (Pit) Log
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Measurement of Speed Doppler Speed Log
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The Distance in yards that a ship travels in 3 minutes (D) is equal to the Ship’s Speed (Spd) in knots multiplied by 100. D = Spd x 100 3 Minute Rule
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The Distance in nautical miles that a ship travels in 6 minutes (D) is equal to the Ship’s Speed (Spd) in knots divided by 10. 6 Minute Rule D = SPD 10
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REVIEW What does a fathometer measure? What does D=Speed x 100 tell you?
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QUESTIONS??
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